This invention relates to an electro-mechanical transducer for tactile stimulation and for tactile sensing. The invention as a tactile display or sensor is suited for use as a computer peripheral or any device requiring the presentation or reception of tactile sensations to or by a user including rehabilitation treatments. Specific embodiments also have applications as a micro-actuator for conveying objects.
Devices have been built in the past to relay tactile information to a subject by mechanical stimulation distributed over a significant area of the skin, usually at the fingertip pad. Such display devices have almost exclusively relied on actuated arrays of raised pins called hereafter xe2x80x9cindentationxe2x80x9d devices. For example in U.S. Pat. No. 4,871,992, Petersen discloses an apparatus which combines electromagnetic transducers and cam transmissions to raise and lower pins under computer control.
Other modes of actuation have been applied to accomplish similar purposes. In U.S. Pat. No. 5,580,251, Gilkes and Cowens describe the application of polar organic gels to create computer controllable raised dots patterns. In U.S. Pat. No. 5,222,895, Fricke discloses a method to use electrorheological fluids to cause raised dots to appear on a flexible surface. A similar arrangement appears in U.S. Pat. No. 5,496,174, Garner.
Piezo ceramics have also shown great utility in achieving similar purposes e.g., U.S. Pat. No. 4,044,350 to Tretiakoff and Tretiakoff and U.S. Pat. No. 4,758,165 to Tiesmans and Zeehuisen which combines piezo ceramics with actuating cantilever reeds in a Braille cell.
Electromagnetic means are disclosed in U.S. Pat. No. 4,586,904 to Chlumsky and in U.S. Pat. No. 3,984,708 to Holmlund and Alden, as well as in U.S. Pat. No. 4,191,945 to Hannen and Charlesworth and in U.S. Pat. No. 5,583,478 to Renzi.
Recently, shape memory alloy actuators have attracted attention for similar purposes, as in U.S. Pat. No. 5,165,897 by Johnson, U.S. Pat. No. 5,685,721 by Decker, and U.S. Pat. No. 5,718,588 by Tretiakoff and Tretiakoff.
These indentation devices create sufficiently loud tactile sensations for relatively large amounts of indentation. A common design specification for such prior art devices is that they provide a quasi-static indenting displacement of the order of one millimetre of vertical displacement.
Another type of display takes advantage of vibrotactile stimulation. With this technique, an array of tactile active sites stimulates a portion of the skin using an array of contactors vibrating at a fixed frequency. This frequency is selected so as to maximize the loudness of the sensation (200-300 Hz). Tactile images are associated, not with the quasi-static depth of indentation, but the amplitude of the vibration. The Optacon(trademark) device is one of the most well know example. Such units, however, also, rely upon indentation to provide a tactile sensation.
Finally a somewhat different principle is disclosed by Asano et al U.S. Pat. No. 5,389,849 to display tactile information by causing standing and traveling waves in a medium. Nevertheless, the medium itself is displaced vertically and provides an indentation stimulation, albeit a laterally displacing indentation stimulation.
To date, most tactile displays rely on skin indentation effected by a collection of controllable raised pins, hence the term shape displays. Thus static indentation is used as the most common mechanism to create tactile displays.
As referenced earlier, a further kind of tactile sensation can be provided, often referred to as xe2x80x9cvibrotactilexe2x80x9d. When a contactor applies a vibratory signal to the skin at a frequency, which may range from a few Hertz to a few kilohertz, a perception is derived which may be described as xe2x80x9cbuzzingxe2x80x9d. Under certain conditions, a dense collection of vibrotactile stimulation sites may provide the sensation of a tactile image. This is principle on which vibrotactile displays operate. Vibrotactile stimulation may also be of impulsive nature.
Nearly all previous tactile display devices to date have relied on skin indentation as opposed to skin stretch to effect sensations. This present invention relies upon the lateral displacement of the skin to create tactile sensations either of shape type or of vibrotactile type. This allows new forms of transducers of convenient size and structure to be employed.
The invention in its general form will first be described, and then its implementation in terms of specific embodiments will be detailed with reference to the drawings following hereafter. These embodiments are intended to demonstrate the principle of the invention, and the manner of its implementation. The invention in its broadest and more specific forms will then be further described, and defined, in each of the individual claims which conclude this Specification.
According to one aspect of the invention a basic electro-mechanical transducer is provided which comprises in one optional simple form, at least one contactor having a contacting tip which is coupled to an associated transducer which serves as a sensor or actuation means to sense or effect lateral displacement of the contacting tip. With a sensate contacted object positioned at the contacting tip of the contactor, lateral displacement of the contacting tip by the contact actuation means will produce a tactile sensation on the sensate object. The effect of the invention is to provide a tactile sensation through the imposition of a stretching or compressing force on the skin (hereafter xe2x80x9cskin stretchxe2x80x9d). Thus tactile sensations are effected through a lateral displacement of portions of the skin or surface of the sensing object.
Preferably, two or more contactors are provided, particularly for tactile stimulators. Tactile display may be limited to a single location stimulated by a pair of contactors or may be provided by a tactile array: a packed array with the individual contactors being driven by a corresponding array of contactor actuatorsxe2x80x94a driving array. By providing for discrete control over individual actuators in the driving array, a variety of motions for various contactors can be provided, resulting in elaborate tactile sensations.
The contacting tips of an array of contactors may be presented in planar alignment or may be shaped in other than a planar alignment. When supported by a pre-formed substrate, these tips may conform to a shape that is ergometrically efficient or which enhances the coupling of the tips with the contacting object, usually the finger pad.
Contactors may be connected to actuators or sensors by couplings which mechanically amplify the displacements produced by the actuators or delivered to the sensors. A variety of devices may be employed as motive sources, including piezo-electric actuators, magnetostrictive actuators, electrostatic actuators, electroactive contractile or electrostriction polymers actuators (e.g. in electron irradiated P(VDF-TrFE) copolymers), heat expansion actuators, variable magnetic reluctance actuators, Lorentz effect actuators, fluid based actuators using cylinders or bladders, and other equivalently acting actuators. Recent developments in thin-film (sol-gel) piezo-electric devices which allow low voltage operation at, e.g. 5-20 volts, are particularly suited for use with the invention. The actuators may provide displacements in any direction so long as these are converted to lateral motion at the contacting tips of the skin contactors.
Many of the same elements will also serve as sensors.
The invention is equally effective at providing for tactile sensing arrays since most actuators can operates as a two way transducer and can be applied as part of a tactile sensing array. By insertion of appropriate filters between the sensing array and the display array selected features of the tactile signal may be enhanced: a tactile microscope so-to-speak.
Thus, the invention in one aspect provides a tactile transducer comprising at least one pair of adjacent contactors, each contactor having a contacting tip separated by a gap from the adjacent contacting tip, said contactor pair being coupled to transducer means to effect or sense relative displacement of said contactors and associated variation of the lateral gap distance between said contacting tips.
The transducer may be in the form of a linear array of transducers wherein multiple transducers define a sequence of gap distances between consecutive contactor tips, said contactor pairs being coupled to a multiple number of transducer means to effect or sense the variations in the inter-tip gap distances in said sequence of gap distances.
Optionally, adjacent contactors are coupled to individual, shared transducer means.
The invention may also be in the form of a transducer interspersed sets of linear transducer arrays defining an area array which includes gap areas, each gap area being surrounded by contactor tips, said contactors being coupled to said transducer means to effect or sense variations of gap areas.
A particular area array incorporates three interspersed sets of linear transducer arrays defining an array of gap areas surrounded by triplets of contactor tips carried by respective contactors, each triplet of contactors being coupled to transducer means to effect or sense variations of gap areas.
Advantageously, contactors may be mounted to associated transducer means so as to mechanically amplify the effect of the lateral displacement of the contactor tips on the transducer means. Further the gap, the gap distances, or the gap areas between contactor tips may be occupied by flexible, resilient, elastic material.
Preferrably, the transducer means operate on the basis of a piezo-electric effect.
The invention also provides a method of creating a tactile display across a plurality of contactors, each contactor having respective contactor tips separated by gaps that are actuable by actuation means, comprising operation of the actuation means to cause the contactor to be laterally displaced in relation to one another, placing a sensate object against said contactor tips to create tactile sensations. such tactile sensations being caused by varying gap distance or the gap distances, or the gap areas between the contactor tips.
In this method as in claim 9 wherein the contactor tips may be actuable by shared actuation means. Further, the gaps may be varied in size as a result of amplified transverse movements of the contactor tips in response to longitudinal movement of the actuation means.